UNIVERSITY    OF    CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT    STATION 

BERKELEY,    CALIFORNIA 


FACTORS   INFLUENCING  THE   QUALITY 

OF   FRESH   ASPARAGUS  AFTER 

IT   IS   HARVESTED 

C.  S.  BISSON,  H.  A.  JONES  and  W.  W.  ROBBINS 


BULLETIN  410 

October,  1926 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1926 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/factorsinfluenci410biss 


FACTORS   INFLUENCING   THE  QUALITY  OF  FRESH 
ASPARAGUS  AFTER  IT  IS  HARVESTED 

C.  S.  BISSON,i  H.  A.  JONES2  and  W.  W.  KOBBINS3 


INTRODUCTION 

Within  the  past  few  years  California  has  taken  a  leading  place  in 
carlot  shipments  of  fresh  asparagus.  Nearly  all  of  these  shipments 
originate  in  the  Sacramento,  San  Joaquin,  and  Imperial  valleys  at 
about  the  same  time  of  the  year.  Asparagus  is  shipped  from  the 
Imperial  Valley  until  about  May  1,  a  date  at  which  the  eastern 
asparagus  is  usually  moved  in  considerably  quantity.  Most  of  the 
growers  in  the  Sacramento  and  San  Joaquin  valleys  stop  cutting  for 
eastern  shipment  when  the  canneries  open,  usually  in  the  early  part 
of  April. 

Cuttings  are  made  whenever  the  spears  are  sufficiently  long.  It 
may  be  necessary  to  harvest  each  day,  or  every  second  or  third  day, 
depending  upon  the  temperature.  The  cut  spears  are  laid  on  the 
ridges  and  gathered  in  lug  boxes  which  are  carried  in  horse-drawn 
sleds  or  carts.  In  the  Imperial  Valley  the  asparagus  is  graded, 
bunched,  and  packed  on  the  individual  ranches.  In  the  delta  region 
of  the  San  Joaquin  and  Sacramento  valleys,  however,  most  of  it  is 
transported  by  truck  or  boat  to  central  packing  houses,  where  it  is 
handled  by  a  few  large  shippers. 

Most  of  the  asparagus  packed  for  eastern  shipment  is  bunched. 
When  brought  to  the  packing  sheds,  the  spears  are  usually  sorted  by 
hand  into  four  or  five  different  grades,  which  are  distinguished  mainly 
on  the  basis  of  size.  The  spears  are  then  tied  in  bunches  of  approxi- 
mately two  and  one-half  pounds  each.  These  are  then  trimmed  to  a 
length  of  about  eight  and  one-half  inches.  The  trimmed  bunches, 
until  packed,  are  usually  stood  on  the  basal  end  in  shallow  pans  in  an 
inch  or  two  of  water,  which  may  or  may  not  be  iced.  When  removed 
from  the  pan,  each  bunch  is  rolled  in  a  stamped  parchment  paper 
wrapper.  The  wrapped  bunches  are  then  packed  in  pyramidal-shaped 
crates  with  the  butts  resting  on  a  layer  of  wet  moss.     It  is  current 


i  Professor  of  Chemistry,  Chemist  in  Experiment  Station. 

2  Associate  Professor  of  Truck  Crops,  Plant  Breeder  in  Experiment  Station. 

3  Associate  Professor  of  Botany,  Botanist  in  Experiment  Station. 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

practice  also  to  place  parchment  paper  on  the  bottom  of  the  box,  so 
that  the  moss  rests  upon  this  paper  rather  than  upon  the  dry  boards 
of  the  box. 

In  early  spring  when  cuttings  are  light  and  before  it  is  possible 
to  obtain  a  sufficient  number  of  crates  to  make  carlot  shipments,  most 
of  the  asparagus  is  shipped  by  express  without  refrigeration.  In  the 
Imperial  Valley,  as  soon  as  carlot  shipments  begin,  the  asparagus  is 
pre-cooled  before  being  loaded  into  iced  cars.  In  northern  California, 
pre-cooling  is  not  necessary,  the  crates  being  loaded  into  iced  cars  as 
soon  as  packed.  The  crates  are  stacked  in  braced  tiers  in  the  car. 
Bunker  icing  is  practiced.  The  bunkers  are  filled  with  ice  several 
times  during  transit  to  eastern  points.  No  ice  is  placed  either  in  the 
container  or  on  top  of  the  load. 


OBJECTS    OF    EXPERIMENT 

In  the  main,  the  present  methods  of  handling  and  shipping 
asparagus  are  satisfactory,  but  there  are  instances  in  which  asparagus 
has  reached  the  eastern  markets  in  an  unsatisfactory  condition. 
Excessive  wilting,  elongation  of  the  spears  accompanied  by  an  open- 
ing up  of  the  heads,  decay  due  to  bacterial  and  fungous  infection,  and 
general  deterioration  in  quality,  have  all  caused  a  certain  amount  of 
loss.  These  losses  have  occasioned  a  general  demand  by  some  of  the 
growers  and  shippers  for  additional  information  as  to  the  factors 
that  influence  the  keeping  of  asparagus  and  its  edible  qualities  after 
harvest. 

The  experiments  reported  in  this  bulletin  were  started  primarily 
to  determine  the  influence  of  different  storage  temperatures  upon  the 
amount  of  water  absorbed  by  the  spears ;  upon  their  rate  of  growth 
(elongation)  ;  and  upon  those  chemical  changes  taking  place  within 
them  which  are  most  responsible  for  their  quality. 


MATERIALS  AND  GENERAL  METHODS  OF  PROCEDURE 

The  asparagus  used  for  these  studies  was  grown  in  the  Delta,  near 
Clarksburg.  The  spears  were  harvested  early  in  the  morning  and 
brought  promptly  into  a  field  packing  shed  where  they  were  loosely 
placed  in  lug  boxes.  The  crates  were  covered  with  moist  burlap  and 
removed  to  a  cold  storage  cellar.  About  four  hours  elapsed  between 
the  time  the  spears  were  cut  and  the  time  they  were  placed  under 
the  storage   conditions   indicated   in  the   experiments.      In   the   cold 


Bull.  410]         FACTORS   INFLUENCING   QUALITY   OF   ASPARAGUS  5 

cellar,  the  spears  were  graded,  bunched,  and  trimmed  to  approxi- 
mately eight  and  one-half  inches  in  length.  All  bunches  were 
weighed,  the  length  of  individual  spears  being  determined  accurately, 
and  then  were  placed  with  their  butts  in  about  one-half  inch  of  water 
and  stored  at  different  temperatures.  It  was  believed  that  more 
uniform  results  would  be  obtained  if  the  spears  were  stood  in  water 
rather  than  upon  wet  moss,  for  the  former  procedure  would  eliminate 
the  possibility  of  an  uncertain  water  supply.  Samples  for  chemical 
and  microchemical  analyses  were  taken  from  the  lot  as  representative 
of  the  condition  of  the  asparagus  as  it  came  from  the  field.  The 
average  temperature  (Fahr.)  of  the  different  storage  rooms  was  as 
follows :  33°,  41°,  56°,  77°,  and  95°.  The  maximum  deviations  from 
these  temperatures  were  about  2°  P.  for  the  33°  room  and  1°  F.  for 
the  41°,  56°,  77°,  and  95°  rooms.  The  storage  rooms  were  not  ven- 
tilated to  allow  air  to  leave  and  enter  freely,  and  furthermore,  the  air 
within  them  was  not  agitated. 

Increase  in  weight  and  length  of  green  asparagus  in  storage  at 
different  temperatures. — When  asparagus  spears  were  stored  with 
their  butts  in  water  or  resting  on  moist  moss,  they  gained  in  weight 
and  in  length  for  a  number  of  days.  The  weight  increase  was  due  to 
the  absorption  of  water,  the  length  increase  to  actual  growth  of  the 
living  spear.     Tables  1  and  2  show  the  results  of  two  different  tests. 

The  spears  stored  at  77°  and  95°  became  moldy  after  a  few  days, 
and  therefore  were  discarded  as  soon  as  infection  was  noted.  In 
Series  II,  spears  were  not  stored  at  these  higher  temperatures. 

The  data  in  tables  1  and  2  show  that  the  rate  of  water  absorption 
and  of  growth  in  length  of  spears  increased  as  the  temperature 
increased.  However,  at  a  temperature  of  33°  F.  there  was  relatively 
little  increase  in  weight  and  length  of  the  spears.  At  all  temperatures, 
the  greates  percentage  of  increase  in  weight  and  length  occurred 
during  the  first  twenty-four  hours.  After  that,  there  was,  with 
slight  irregularities,  a  slowing  down  in  the  rate.  These  relations  are 
graphically  shown  in  figures  1  and  2. 

The  differences  between  the  corresponding  columns  in  Series  I 
and  II  are  due  in  part,  at  least,  to  differences  in  the  average  sizes  of 
the  two  lots  of  spears.  A  comparison  of  small  and  large  spears  showed 
that  spears  of  small  diameter  grow  more  rapidly  in  length  than  those 
of  large  diameter.  The  average  increase  in  length  per  spear  of  a 
certain  lot  of  small  spears  for  a  seven  day  period  was  20.7  mm., 
whereas  that  of  a  certain  lot  of  large  spears  under  similar  storage 
conditions  for  the  same  period  was  17.5  mm. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE   1 

Increase  in  Weight  and  Length  of  Green  Asparagus  Stored  at  Different 
Temperatures.     Butts  in  Water.     Series  I. 


Date 

Tempera- 
ture 
Fahr. 

Num- 
ber of 
spears 

Total 

weight 

Gms. 

Per  cent 
water 

Per  cent 

increase  in 

weight 

Total 

length 

mm. 

Total 

increase  in 

length 

mm. 

Average 

increase  in 

length  per 

spear 

mm. 

May 

2 

33° 

18 

659.4 
689.9 

92.6 
92.93 

3979 
4010 

3 

4.6 

31 

1.72 

4 

697.0 

93.00 

5.7 

4022 

43 

2.38 

5 

702.1 

93.05 

6.5 

4026 

47 

2.60 

6 

705.2 

93.08 

6.9 

4026 

47 

2.60 

7 

709.7 

93.12 

7.6 

4017 

48 

2.66 

8 

711.9 

93.15 

8.0 

4039 

60 

3.33 

9 

713.5 

93.16 

8.2 

4043 

64 

3.55 

2 

41° 

20 

714.2 

92.60 

4468 

3 

761.6 

93.06 

6.6 

4597 

129 

6.45 

4 

769.1 

93.13 

7.7 

4630 

162 

8.10 

5 

775.8 

93.19 

8.6 

4676 

203 

10.40 

6 

777.3 

93.20 

8.8 

4678 

210 

10.50 

7 

778.8 

93.21 

9.0 

4698 

230 

11.50 

8 

780.0 

93.24 

9.2 

4698 

230 

11.50 

9 

779.8 

93.22 

9.2 

4701 

233 

11.6 

2 

56° 

16 

681.6 

92.6 

3532 

3 

757.1 

93.34 

11.0 

3804 

272 

17.0 

4 

772.5 

93.48 

13.3 

3841 

319 

19.9 

5 

776.8 

93.51 

14.0 

3912 

380 

23.7 

6 

779.3 

93.53 

14.3 

3930 

398 

24.9 

7 

779.1 

93.53 

14.3 

3933 

401 

25.0 

8 

781.8 

93.55 

14.7 

3933 

401 

25.0 

9 

778.1 

93.52 

14.1 

3939 

407 

25.4 

2 
3 

77° 

20 

689.5 

92.60 

4437 

767.5 

93.36 

11.3 

4765 

328 

16.4 

4 

767.7 

93.36 

11.3 

4767 

330 

16.5 

5 

766.5 

93.35 

11.2 

4808 

371 

18.5 

6 

712. 5 

92.84 

3.3 

4807 

370 

18.5 

2 

95° 

15 

596.5 

92.60 

3355 

3 

671.1 

93.41 

12.4 

3809 

254 

16.90 

4 

668.0 

93.38 

11.9 

3617 

262 

17.45 

5 

650.0 

93.20 

8.9 

3625 

270 

18.00 

BULL.  410]         FACTORS   INFLUENCING   QUALITY   OF   ASPARAGUS 


TABLE   2 

Increase  in  Weight  and  Length  of  Green  Asparagus  Stored  at  Different 
Temperatures.     Butts  in  Water.     Series  II. 


Date 

Tempera- 
ture 
Fahr. 

Number 
of 

spears 

Total 

weight 

Gms. 

Per  cent 

increase  in 

weight 

Total 

length 

mm. 

Total 

increase  in 

length 

mm. 

Average 

increase  in 

length  per 

spear 

mm. 

June 

9 

33° 

16 

754.1 

3495 

10 

770.4 

2.1 

3519 

24 

1.5 

11 

772.8 

2.4 

3529 

34 

2.13 

12 

774.0 

2.6 

3530 

35 

2.19 

13 

781.1 

3.5 

3530 

35 

2.19 

14 

787.6 

4.4 

3532 

37 

2.31 

15 

795.3 

5.5 

3535 

40 

2.5 

16 

800.0 

6.1 

3535 

40 

2.15 

9 

41° 

17 

738.2 

3726 

10 

785.6 

6.4 

3838 

112 

6.58 

11 

796.1 

7.8 

3866 

140 

8.23 

12 

800.0 

8.3 

3875 

149 

8.76 

13 

802.1 

8.6 

3888 

162 

9.52 

14 

802.2 

8.7 

3908 

182 

10.70 

15 

803.3 

8.9 

3910 

184 

10.82 

18 

804.0 

10.2 

3913 

187 

11.00 

9 

56° 

18 

773.2 

3978 

10 

847.5 

9.6 

4218 

240 

13.33 

11 

858.5 

11.3 

4238 

260 

14.44 

12 

862.4 

11.5 

4254 

276 

15.33 

13 

862.8 

11.6 

4288 

310 

17.22 

14 

863.1 

11.7 

4288 

310 

17.22 

15 

863.4 

11.7 

4296 

318 

17.67 

16 

864.6 

11.8 

4298 

320 

17.77 

In  1917,  Morse2  conducted  experiments  in  keeping  asparagus  after 
cutting.  The  spears  were  stored  under  a  variety  of  conditions,  as 
follows : 

1.  Butts  in  shallow  water,  at  laboratory  temperatures  (70°  to 
80°  P.). 

2.  Butts  in  shallow  water,  in  refrigerator  (45°  to  50°  P.). 

3.  Wrapped  loosely  in  paper,  and  laid  on  shelf,  at  laboratory 
temperature  (70°  to  80°  P.). 

4.  Wrapped  loosely  in  paper,  and  laid  on  shelf  in  refrigerator 
(45°  to  50°  P.). 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


/s 

)  ^° 

/4- 
/3 

ta 

tt 

,4t° 

1  y 

S    7 

Q3      6 

1, 

>JJ° 

/ 
0, 

0  12  3         4^67 

Days 

Fig.  1. — Percentage  increase  in  weight  of  green  asparagus. 


BULL.  410]         FACTORS   INFLUENCING    QUALITY   OF   ASPARAGUS 


AVERAGE 

/NCPEA3E  //V  LENGTH  PEP  3PEAP 

£6 

>SG° 

a4 

2B 

EO 

IS 

If) 

< 

Si 

\4/° 

|    10 

3 

6 

4 

33° 

a 

o  < 

O  /  8  3         4  S         6 

Ool/3 

Fig.  2. — Average  increase  in  length  per  spear 


7        3 


10  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

5.  Laid  directly  on  cake  of  ice  (no  temperature  indicated). 

6.  Stood  upright  in  tin  box  with  a  tight  cover,  and  with  no  water ; 
box  and  contents  placed  in  refrigerator  (45°  to  50°  F.). 

Morse's  results  show  that  all  spears,  except  those  with  the  butts 
in  water,  lost  in  fresh  weight  during  the  storage  period.  Even  those 
laid  directly  on  ice  or  kept  in  a  tin  box  with  a  tight  cover,  lost  from 
2  to  5  per  cent  in  fresh  weight.  The  data  also  show  that  the  growth 
rate  of  the  spears  when  stored  with  the  butts  in  water  increases  with 
an  increase  in  the  temperature.  For  example,  the  average  increase 
in  length  per  spear  for  a  10-hour  period  was  2.6  mm.  at  45°  F., 
4.0  mm.  at  49°-54°  F.,  12.3  mm.  at  75°-76°  P.,  and  18.6  mm.  at  80°  F. 


INFLUENCE  OF   DIFFERENT  STORAGE  TEMPERATURES    UPON 
STRUCTURAL  CHANGES  OF   GREEN   ASPARAGUS 

It  is  well  to  have  in  mind  the  structure  of  the  edible  asparagus 
spear  before  discussing  the  morphological  changes  which  it  undergoes 
after  it  is  harvested. 

Structure  of  the  spear. — The  general  structure  of  the  asparagus 
shoot  may  be  seen  from  a  study  of  figure  3.  The  following  are  the 
principal   anatomical   regions : 

1.  Epidermis. 

2.  Cortex. 

3.  Pericyclic  fibers. 

4.  Ground  parenchyma  tissues. 

5.  Vascular  bundles,  scattered  through  the  parenchyma. 
Epidermis. — This  consists  of  a  single  layer  of  cells.     The  outer 

wall  of  the  epidermal  cells  is  thicker  than  the  inner  and  side  walls; 
it  is  somewhat  cutinized,  thus  rendering  it  impervious  to  the  passage 
of  water.  In  the  epidermis  of  a  shoot  are  found  numerous  pores  or 
stomata.  Each  stoma  is  bordered  by  two  kidney-shaped  epidermal 
cells,  the  guard  cells.  These  differ  from  all  other  epidermal  cells  not 
only  in  shape,  but  in  that  they  possess  chlorophyll,  and  in  the  ability 
to  change  shape.  It  is  through  these  pores  that  the  gases,  carbon 
dioxide,  and  ox3rgen,  pass  into  and  out  of  the  shoot,  and  the  water 
vapor  moves  outward. 

Cortex. — The  cortex  is  a  zone  of  tissue  of  varying  width,  consist- 
ing of  rather  large,  thin-walled  cells,  which  do  not  fit  closely  together 
but  have  air  spaces  between  them.  It  is  these  cells  of  the  green  stem 
which  possess  the  green  coloring  material  (chlorophyll). 


BULL.  410]       FACTORS  influencing  quality  of  asparagus  11 

Pericyclic  fibers. — The  pericyclic  fiber  zone  is  composed  of  long, 
tapering  thick-walled  cells  (fibers),  which  fit  closely  together,  leaving 
no  intercellular  spaces  between  them.  The  fiber  cells  have  flat  sur- 
faces, with  sharp  angles.  The  walls  of  old  pericyclic  fibers  have 
deposited  within  them  a  material  known  as  lignin,  which  gives  hard- 
ness to  this  tissue. 

It  should  be  mentioned  at  this  point  that  the  toughness  of  an 
asparagus  shoot  is  in  large  part  due  to  the  hardness  of  the  lignified 


Fig.  3. — Cross-section  near  the  tip  of  an  asparagus  spear,     e,  epidermis ; 
c,  cortex;  p,  pericycle;  v,  vascular  bundles;  g,  ground  tissue. 

walls  in  these  fibers.  In  most  canneries  a  grade  known  as  ' '  stripped ' ' 
or  "peeled"  asparagus  is  canned.  Only  the  very  large  spears  are 
used  in  this  grade.  Each  spear  is  scraped  with  a  knife,  in  which 
process,  the  epidermis,  cortex,  and  pericyclic  fibers  are  removed.  The 
removal  of  the  pericyclic  fibers  eliminates  the  principal  structural 
elements  responsible  for  toughness. 

It  will  be  observed  from  figure  3  that  in  the  tip  of  the  asparagus 
shoot,  the  walls  of  the  fibers  are  thin ;  moreover,  no  lignin  is  deposited 
within  them.  Also  it  will  be  noted  that  there  is  no  sharp  line  of 
demarkation  between  the  parenchyma  tissue  of  the  cortex  and  that 


12 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


which  is  destined  to  develop  into  pericyclic  fibers.  As  the  stem  grows 
older,  the  fiber  region  becomes  more  and  more  distinct  from  the 
adjoining  parenchyma   (fig.  4). 


Fig.  4. — Cross-section  near  the  base  of  an  asparagus  spear. 
Labelling  as  under  fig.  3,  above. 

Ground  parenchyma. — This  name  is  applied  to  the  central  part  of 
the  stem  inside  the  pericyclic  fiber  zone.  The  cells  composing  this 
tissue  are  large  and  thin-walled,  and  are  separated  by  large  inter- 
cellular spaces.  The  vascular  bundles  are  scattered  throughout  this 
area,  except  for  a  central  region  with  indefinite  boundaries,  in  which 


BULL.  410]         FACTORS   INFLUENCING    QUALITY   OF   ASPARAGUS 


13 


bundles  are  lacking*.  The  vascular  bundles  near  the  fibers  are  the 
youngest  and  smallest ;  they  increase  in  age  and  size  as  the  center  of 
the  stem  is  approached. 

Vascular  bundle. — Each  vascular  bundle  appears  in  cross  section 
as  a  V-form  (fig.  5),  with  the  apex  directed  toward  the  center  of  the 
stem.  The  tracheal  tubes  form  the  arms  of  the  bundle,  and  between 
them  are  the  phloem  elements.  The  tracheal  tubes  of  a  bundle  are 
smallest  at  the  point  of  the  bundle,  usually  becoming  larger  as  the 


Fig.  5. — Cross-section  of  single  vascular  bundle  from  asparagus  spear.     Note 
the  large  lignified   (shaded)   water  conducting  tubes. 

ends  of  the  arms  are  approached.  Associated  with  the  tracheal  tubes 
are  thick-walled  wood  fibers.  The  tracheal  tubes  are  chiefly  of  the 
reticulate  type ;  a  few  of  the  smaller  have  spiral  thickenings. 

Anatomical  changes  which  take  place  as  the  stem  grows  older. — 
One  may  follow  the  anatomical  changes  which  take  place  in  the  aspar- 
agus spear  b}^  a  study  of  successive  sections  from  the  tip  towards  the 
butt  (fig.  6).  Normally,  under  field  conditions,  the  following  struc- 
tural changes  occur  as  the  spear  grows  older : 

(a)  The  outer  wall  of  the  epidermis  becomes  thicker  and  more 
heavily  cutinized,  and  hence  probably  more  impervious  to  loss  of 
water. 


14 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


(&)  The  fiber  zone  becomes  more  distinct  from  the  adjoining 
parenchyma  tissue,  and  the  fiber  walls  become  thicker  and  more 
heavily  lignified. 


Fig.  6. — A,  cross-section  of  asparagus  spear  near  tip;  B,  same,  at  about  the 
middle;  C,  same  near  the  base;  D,  vascular  bundle  bordering  pith  from  section 
A;  E,  same  from  section  B;  F,  same  from  section  C.  In  D,  E,  and  F,  the 
shaded  portions  indicate  lignified  elements. 

(c)  There  is  an  increase  in  the  number  of  lignified  tracheal  tubes 
and  a  thickening  of  their  walls.  If  sections  are  taken  at  various  dis- 
tances from  the  tip  of  an  asparagus  shoot,  it  will  be  observed  that  the 


BULL.  410]         FACTORS   INFLUENCING    QUALITY   OF   ASPARAGUS  15 

nearer  the  base  they  are  taken,  the  greater  is  the  number  of  lignified 
elements  in  the  vascular  bundles  (fig.  6).  For  example,  in  freshly 
harvested  shoots,  the  average  number  of  lignified  elements  in  the 
innermost  vascular  bundles  of  sections  near  the  tip  (young  portion 
of  shoots)  was  found  to  be  9  ;  in  sections  of  the  same  shoot  taken  about 
half  way  between  the  tip  and  the  butt,  11.5 ;  and  in  sections  taken 
at  the  base  (oldest  portion  of  shoots)  17.6. 

Duplicate  lots  of  asparagus  spears  similar  to  those  used  in  Series  I 
and  II,  were  stored  at  different  temperatures,  with  the  butts  in  about 
one-half  inch  of  water.  Spears  were  taken  from  each  storage  tem- 
perature at  24-hour  intervals  and  examined  anatomically.  Transverse 
sections  of  three  different  parts  of  representative  spears  were  taken, 
as  follows :  Section  I  about  1  cm.  from  the  tip  in  the  tender,  green 
part  of  the  spear ;  section  II  about  10  cm.  from  the  tip  in  the  purple 
part  of  the  spear;  and  section  III,  approximately  15  cm.  from  the 
tip  in  the  more  mature,  fibrous,  and  white  portion  of  the  spear. 

The  sections,  cut  free  hand,  were  placed  immediately  in  an 
alcoholic  solution  of  phloroglucin  (phloroglucin  1  gm.,  95  per  cent 
alcohol  100  cc),  and  left  five  minutes.  They  were  then  transferred 
to  25  per  cent  hydrochloric  acid  for  a  period  of  ten  to  fifteen  minutes. 
All  lignified  membranes  stained  red.  The  degree  of  lignification  was 
roughly  indicated  by  the  shade  of  red ;  membranes  slightly  lignified 
were  pink  or  light  red,  and  those  heavily  lignified  dark  red. 

Safranin  was  also  tested  as  a  lignin  stain,  but  it  proved  less  satis- 
factory than  phloroglucin.  Safranin  stains  cellulose  walls  as  well  as 
lignified  walls,  but  with  alcohol,  washes  out  of  the  former  much  more 
readily  than  from  the  latter.  However,  unless  differentiation  is 
uniform  in  all  sections,  there  is  danger  of  being  misled. 

The  degree  of  lignification  was  determined  by  counting  the  number 
of  lignified  tracheal  tubes  in  the  oldest  vascular  bundles,  which  are 
those  bordering  the  central  parenchyma  tissue;  also,  by  noting  the 
color  of  the  pericycle,  and  of  the  cells  bordering  the  tracheal  tubes. 
In  each  section  examined,  of  which  there  were  many  hundreds,  the 
number  of  lignified  tracheal  tubes  in  from  five  to  ten  vascular  bundles 
was  ascertained.  This  variation  resulted  from  the  fact  that  the  num- 
ber of  vascular  bundles  of  the  inner  ring  was  not  always  the  same, 
and  also  that  only  those  bundles  were  considered  in  which  the  lignified 
elements  could  be  counted  with  accuracy. 

It  will  be  seen  from  these  figures  that  under  the  conditions  of 
storage,  lignification  took  place  the  full  length  of  the  shoot  and  at  all 
temperatures,  in  general  being  less  at  low  temperatures  than  at  high, 


16 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


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BULL.  410]         FACTORS   INFLUENCING    QUALITY   OF   ASPARAGUS 


17 


and  less  at  the  tip  of  the  spear  than  at  the  butt.  The  discrepancies 
occasionally  appearing  in  the  figures  are  believed  to  be  due  partly  to 
individual  variation,  partly  to  the  inability  to  select  shoots  which  are 
of  exactly  the  same  age,  and  partly  to  the  difficulty  of  making  sections 
at  comparable  parts  of  the  spear.  In  addition  to  lignification  which 
takes  place  in  the  bundles,  there  was  also  progressive  lignification 
of  the  fibers  in  the  pericycle,  and  of  the  elements  immediately 
surrounding  the  vascular  bundles.  In  these  cases,  also  lignification 
progressed  more  rapidly  at  high  than  at  low  temperatures,  and  at  the 


TABLE  4 

Average  Number  Lignified  Tracheal  Tubes  in  Inner  Vascular  Bundles  of 

Asparagus  Spears  Stored  at  Different  Temperatures. 

Degrees  F.   (Series  II) 


Number  of 

Section  I  (Tip) 

Section  II  (Middle) 

Section  III  (Base) 

days 
stored 

33° 

41° 

56° 

33° 

41° 

56° 

33° 

41° 

56° 

0 

12.6 

12.6 

12.6 

21.1 

21.1 

21.1 

29.9* 

29.9* 

29.9* 

1 

13.8 

11.4 

11.6 

24.4 

24.6 

23.8* 

32.6* 

33.6* 

32.8* 

2 

14.0 

12.6 

13.0 

23.0 

27.6* 

21.2* 

33.2* 

32.0* 

35.2* 

3 

11.0 

8.2 

10.4 

12.8* 

25.6* 

24.6* 

33.4* 

35.2| 

31.8J 

4 

14.2 

14.2 

13.2 

24.6* 

26.8* 

27.8* 

31.2* 

35. 2\ 

33. 7J 

5 

14.2 

14.4 

15.4 

34.0* 

27.4* 

26.6* 

32.4* 

35. 0| 

38. 6J 

6 

14.8 

14.0 

15,2 

33.6* 

28.8* 

28.8* 

43.6| 

39. 2t 

39. 8  J 

*  Pericyclic  fibers  lignified. 

%  Lignification  of  cells  surrounding  the  vascular  bundles  in  addition  to  that  of  pericyclic  fibers. 

base  of  the  shoots  than  at  the  tip.  Attention  is  called  to  the  fact  that 
the  most  pronounced  lignification  took  place  the  first  24  hours  after 
the  spears  were  placed  in.  storage.  It  should  also  be  noted  that  at  the 
end  of  the  seventh  day  of  storage,  although  an  increase  in  toughness 
was  evident,  no  pronounced  bitterness  had  developed  in  any  of  the 
lots  stored  at  33°,  41°,  and  56°  F.   . 

Bitting1  studied  the  anatomical  changes  in  white  asparagus  after 
.harvest.  The  results  obtained  are,  in  general,  similar  to  those  reported 
herein.  However  >  it  is  of  interest  to  note  that  Bitting  finds  in  a  com- 
parison of  "etiolated"  (white)  and  "green"  spears,  that  the  former 
"showed  more  lignification,  indicating  that  the  green  stalks  are  in 
better  condition  to  resist  the  traumatic  effects  resulting  from  the 
cutting,  at  least  for  the  first  days." 

Considering  the  data  cited  above,  and  the  results  obtained  by 
Bitting,  it  is  seen  that  asparagus  spears  begin  to  deteriorate  in  quality, 


18  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

as  evidenced  by  the  degree  of  lignification,  immediately  after  they  are 
cut,  and  that  deterioration  is  most  rapid  during  the  first  24  hours, 
after  which  time  the  process  continues  at  a  decreased  rate.  Deteriora- 
tion progresses  at  all  temperatures,  even  at  33°  F ;  it  is  less,  however, 
at  low  than  at  high  temperatures. 


INFLUENCE  OF  DIFFERENT  STORAGE  TEMPERATURES  UPON  THE 
CHEMICAL  COMPOSITION  OF  GREEEN   ASPARAGUS 

General  Methods 

Preparation  and  storage  of  samples. — The  bulk  composite  sample 
of  asparagus  as  obtained  from  the  field  was  divided  into  lots  contain- 
ing from  18  to  20  spears,  and  cut  to  a  length  of  about  eight  and  one- 
half  inches.  Care  was  taken  to  make  the  lots  as  nearly  alike  in  all 
respects  as  possible.  They  were  then  placed  in  800  cc.  beakers  with 
the  butt  ends  resting  in  about  one-half  inch  of  distilled  water.  One 
of  the  lots  was  preserved  shortly  after  harvesting.  The  remaining 
lots  were  placed  in  the  different  storage  rooms. 

Preparation  of  the  samples  for  analysis. — One  of  the  lots  of 
asparagus  was  removed  from  each  storage  room  every  24  hours  and 
preserved  immediately.  Before  preserving,  the  spears  were  wiped  to 
remove  grit  and  water.  Samples  were  removed  every  24  hours  for 
four  days  except  from  the  95°  F.  room.  The  spears  stored  at  the 
latter  temperature  were  starting  to  rot  by  the  fourth  day  and  there- 
fore were  not  preserved.  The  spears  were  cut  into  one  inch  lengths 
and  placed  in  storage  flasks.  They  were  weighed,  0.25  gm.  of  CaC03 
added,  and  then  enough  redistilled  95  per  cent  alcohol  added  to  make 
the  final  solution  about  60  per  cent  alcohol  by  volume.  The  flasks 
were  placed  in  a  water  bath,  heated  to  boiling,  and  the  material  boiled 
slowly  with  a  reflux  condenser  for  five  minutes.  The  flasks  were 
stoppered  white  hot.  The  samples  were  then  stored  in  this  condition 
at  room  temperature  until  they  were  analyzed. 

The  preserved  samples  were  analyzed  for  dry  matter,  reducing 
substances  (chiefly  sugars),  total  sugars,  and  crude  fiber. 

Dry  matter. — The  weights  of  the  dry  material  from  the  samples 
were  obtained  in  the  following  manner.  The  alcoholic  extract  was 
evaporated  on  a  water  bath  until  a  thick  syrupy  liquid  remained  in 
the  dish.  The  spears  were  cut  lengthwise  into  strips  and  then  placed 
in  the  evaporating  dishes  containing  the  residue  from  their  alcoholic 
extracts.    By  cutting  the  solid  material  into  thin  strips  much  time  was 


Bull.  410 


FACTORS   INFLUENCING    QUALITY   OF   ASPARAGUS 


19 


saved  in  drying  the  samples,  and  also  in  grinding  the  material  after 
it  was  dry.  The  dishes  containing  the  solid  material  were  again  placed 
on  the  water  bath  and  heated  until  most  of  the  water  and  alcohol  were 
evaporated.  The  dishes  were  then  placed  in  an  electric  oven,  operated 
at  55°  C.  (131°  F.).  After  48  hours  in  the  oven,  the  samples  were 
taken  out,  and  the  last  traces  of  volatile  substances  removed  in  a 
vacuum  oven  at  60°  C.  (140°  F.).  The  dishes  and  contents  were 
brought  to  constant  weight.  The  weight  of  the  dry  matter  was  then 
corrected  for  the  added  CaC03.  The  percentage  of  dry  matter  in  the 
total  sample  of  asparagus  for  each  day  at  the  various  storage  tempera- 
tures is  given  in  table  5.  These  results  are  represented  graphically  in 
figure  7. 

TABLE  5 
Percentage  of  Dry  Matter 


Period  of 
storage 

Original 
sample 

Storage  temperatures  (Fahr.) 

in  hours 

33° 

41° 

56° 

77° 

95° 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

0 

7.45 

24 

7.17 

6.87 

6.31 

6.39 

6.25 

48 

7.06 

6.56 

6.18 

5.99 

6.01 

72 

6.91 

6.55 

6.07 

5.85 

5.86 

96 

6.87 

6.56 

6.25 

5.89 

•-  •— *j~=.— . ,      ^Ay'  ^ 


-95° 


77, 


BA  43  72 

Period  of  storage  in  hours 


96 


Fig.   7. — Percentage  of  dry  matter. 


20 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


The  values  given  in  table  6  for  the  percentage  decrease  of  dry 
matter  at  the  end  of  each  24-hour  period  for  each  storage  temperature 
were  calculated  from  the  data  in  table  5  by  dividing  the  differences 
between  the  percentage  of  dry  matter  at  the  end  of  each  24-hour 
interval  and  the  percentage  of  dry  matter  in  the  original  sample,  by 
the  percentage  of  dry  matter  in  the  original  sample.  These  values  are 
plotted  in  figure  8  against  the  period  of  storage  in  hours. 


TABLE  6 
Percentage  Decrease  of  Dry  Matter 


Storage  period 

Storage  temperatures  (Fahr.) 

in  hours 

33° 

41° 

56° 

77° 

95° 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

24 

3.8 

7.8 

15.3 

14.2 

16.1 

48 

5.2 

11.9 

17.0 

19.6 

19.3 

72 

7.3 

12.1 

18.5 

21,5 

21.3 

96 

7.8 

11.9 

16.1 

20.9 

O  £A  46  7E  96 

Period  of  storage  in  hours 

Fig.  8. — Percentage  decrease  of  dry  matter. 

It  will  be  observed  that  the  rate  of  decrease  of  dry  matter  is 
smallest  in  the  samples  stored  at  33°  F.  and  that  this  rate  increases 
with  considerable  uniformity  as  the  temperature  becomes  higher. 
The  decrease  in  the  percentage  of  dry  matter  is  due  to  the  absorption 
of  water  and  probably  to  the  destruction  of  sugars  by  respiration,  the 
former  probably  being  chiefly  responsible. 


BULL.  410]         FACTORS   INFLUENCING    QUALITY   OF   ASPARAGUS 


21 


Sugars. — Sugars  are  important  constituents  of  asparagus,  deter- 
mining to  a  degree  its  food  value  and  edible  quality.  Moreover,  the 
reducing  sugars  are  the  chief  substances  from  which  cell  wall  mate- 
rials and  other  more  complex  plant  substances  are  made;  and,  too, 
the  foods  mainly  used  in  respiration  are  sugars.  Consequently,  sugar 
values  at  intervals  are  probably  a  partial  measure  of  the  edible  quality 
and  of  the  food  value  of  the  spears,  and  show  the  trend  of  important 
chemical  transformations  going  on  in  the  plant. 

After  the  dry  weights  were  obtained,  the  samples  were  ground  and 
passed  through  an  80-mesh  sieve,  dried  again  for  12  hours  in  a  vacuum 
oven,  and  stored  in  tightly  stoppered  tubes  in  a  desiccator  until 
analyzed. 

The  determinations  of  free  reducing  substances  (chiefly  sugars) 
and  total  sugars  wTere  made  on  alcoholic  extracts  of  the  original  pre- 

TABLE  7 
Percentage  of  Free  Reducing  Substances   (On  Dry  Weight  Basis) 


Period  of 

Original 
sample 

Storage  temperatures 

(FatnO 

storage 
in  hours 

33° 

41° 

56° 

77° 

95° 

0 

Per  cent 

23.1 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

24 

23.30 
22.53 
21.35 
19.87 

21.21 
21.93 
21.08 
17.70 

19.62 
19.92 

18.89 
16.27 

18.82 
18.36 
17.36 
14.90 

18  27 

48 

14.87 

72 

14.90 

96 

24  46  72 

Per/od   of~  storage  in  hours 

Fig.  9. — Percentage  of  free  reducing  substances   (chiefly  sugars). 


22 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


pared  samples.  The  alcoholic  extracts  were  anatyzed  for  their  sugar 
contents,  using  the  gravimetric  method  of  Munson  and  Walker3. 
The  results  of  the  analyses  for  free  reducing  substances  are  given  in 
table  7  and  are  plotted  in  figure  9  against  the  storage  period  in  hours. 
The  data  given  in  table  8,  calculated  from  those  given  in  table  7, 
show  the  total  percentage  decrease  of  reducing  substances  at  each  tem- 
perature at  the  end  of  every  24-hour  interval.  These  values  are 
represented  graphically  in  figure  10. 


TABLE  8 
Percentage  Decrease  of  Free  Eeducing  Substances 


Period  of 

Storage  temperatures  (Fahr.) 

storage 

in  hours 

33° 

41° 

56° 

77° 

95° 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

24 

—0.8 

8.2 

15.1 

18.5 

20.9 

48 

2.5 

5.1 

13.8 

20.5 

35.6 

72 

7.6 

8.7 

18.2 

24.9 

35.5 

96 

14.0 

23.4 

29.6 

35.5 

0  24  48  72 

Period  of  storage  in  hours 

Fig.  10. — Percentage  decrease  of  reducing  substances  (chiefly  sugars) 


It  will  be  seen  from  the  values  given  in  tables  7  and  8,  and  from 
figures  9  and  10  that,  with  the  exception  of  the  samples  stored  at 
33°  F.,  all  show  a  very  rapid  decrease  in  reducing  substances  during 


BULL.  410]         FACTORS   INFLUENCING    QUALITY   OF   ASPARAGUS 


23 


the  first  24  hours  of  storage.  With  the  exception  of  the  95°  F.  curve, 
the  rates  of  decrease  in  reducing  substances  are  relatively  large  even 
during  the  last  24  hours  in  storage.  At  the  end  of  96  hours  the  sugar 
content  of  the  samples  stored  below  95°  F.  did  not  drop  below  the 
percentage  present  in  the  95°  F.  sample  at  the  end  of  48  hours.  At 
95°  F.,  asparagus  spears  lost  over  20  per  cent  of  their  reducing  sub- 
stances during  the  first  24  hours,  an  amount  which  exceeds  by  about 
7  per  cent  that  lost  by  spears  stored  at  33°  F.  at  the  end  of  96  hours. 

The  results  of  the  analyses  for  total  sugars  are  given  in  table  9 
and  are  represented  graphically  in  figure  11. 

The  curves  (fig.  11)  have  nearly  the  same  form  as  those  (fig.  9)  for 
reducing  substances.  The  rate  of  loss  of  total  sugars  with  increas- 
ing temperatures  is  also  very  similar  to  that  of  the  reducing  sub- 

TABLE  9 

Percentage  of  Total  Sugars  (on  Dry  Weight  Basis) 


Period  of 
storage  in  hours 

Original 
sample 

33° 

41° 

56° 

77° 

95° 

0 

Per  cent 

24.91 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

24 

26.69 
26.37 
24.76 
23.91 

23.59 
24.58 
23.63 
21.08 

22.05 
21.49 
21.32 
18.21 

20.09 
20.28 
18.08 
16.41 

19.63 

48 

16.34 

72 

16.75 

96 

2A  *a 

Period  of  sforoqe  Jn  hours 

Fig.  11. — Percentage  of  total  sugars. 


24 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


stances.  It  is  worthy  of  note  that  at  a  storage  temperature  of  33°  F., 
there  is  no  loss,  but  rather  a  slight  increase,  in  both  the  reducing 
substances  and  the  total  sugars  during  the  first  24  hours,  after  which 
time  there  is  a  decrease.  It  will  be  observed  that  reducing  sugars 
constitute  approximately  90  per  cent  of  the  total  sugar  in  the  dry 
matter.  Under  the  various  storage  conditions  of  his  experiment, 
Morse  (loc.  cit.)  found  losses  of  the  total  sugar  in  the  dry  matter, 
the  values  being  greater  at  room  temperature  than  at  those  which 
prevailed  in  the  refrigerator. 

Crude  fiber. — The  percentage  of  crude  fiber  gives  an  indication  of 
the  "toughness"  of  asparagus.  The  total  percentages  of  crude  fiber 
for  each  storage  temperature  are  given  in  table  10  and  are  plotted  in 
figure  12. 

TABLE  10 
Percentage  of  Crude  Fiber   (On  Dry  Weight  Basis) 


Storage  period 

Original 
sample 

Storage  temperatures  (Fahr.) 

in  hours 

33° 

41° 

56° 

77° 

95° 

0 

Per  cent 

8.88 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

24 

9.24 
9.35 
9.91 
9.67 

10.54 
10.26 
10.06 
10.52 

11.22 
11.76 
11.36 
11.91 

11.97 
12.63 
12.53 
14.02 

12.44 

48 

13.05 

72 

13.56 

96 

46  72 

Period  of  storage  /n  hours 

Fig.  12. — Percentage  of  crude  fiber. 


Bull.  410]         FACTORS   INFLUENCING   QUALITY   OF   ASPARAGUS 


25 


The  curves  indicate  a  very  marked  increase  in  the  crude  fiber  in 
asparagus  under  different  temperature  conditions.  The  results  in 
general  are  in  accord  with  those  obtained  by  microchemical  tests,  as 
shown  on  pages  16  and  17.  The  percentage  increase  of  crude  fiber 
under  different  storage  conditions  is  given  in  table  11,  and  graphically 
represented  in  figure  13. 

TABLE  11 

Percentage  Increase  of  Crude  Fiber  (On  Dry  Weight  Basis) 


Period  of 

Storage  temperatures  (Fahr.) 

storage  in  hours 

33° 

41° 

56° 

77° 

95° 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

24 

4.1 

18.7 

26.4 

34.8 

40.1 

48 

5.3 

15.5 

32.4 

42.3 

47.0 

72 

11.6 

13.3 

27.9 

41.1 

52.7 

96 

8.9 

18.1 

34.1 

49.0 

£4  43  78 

Period  or  storage  in  hours 

Fig.  13. — Percentage  increase  of  crude  fiber. 


The  greatest  percentage  change  takes  place  during  the  first  24 
hours  of  storage,  and  for  the  higher  temperatures  the  rate  of  change 
decreases  with  the  length  of  time  in  storage.  It  will  be  noted  that  as 
the  crude  fiber  increases,  the  sugar  decreases.  The  development  of 
the  former  is  probably  at  the  expense  of  sugar.  Morse  (loc.  cit.)  cites 
a  positive  gain  in  the  absolute  amount  of  crude  fiber  in  asparagus 


26  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

spears  after  they  were  harvested.  At  a  temperature  of  70°  to  80°  F., 
with  the  butts  in  water,  the  percentage  of  fiber  in  the  dry  matter 
changed  from  10.54  to  15.51  in  72  hours,  whereas  at  a  temperature  of 
45°  to  50°F.  the  change  was  from  10.54  to  12.71  during  the  same 
interval. 


DISCUSSION  AND  SUMMARY 

1.  After  asparagus  is  harvested,  changes  occur  in  its  structure  and 
chemical  composition,  which  affect  its  edible  qualities. 

2.  The  principal  changes  reported  in  this  paper  concern  growth 
in  length,  weight,  dry  matter,  reducing  substances,  total  sugars,  and 
crude  fiber.  Crude  fiber,  which  is  reflected  in  the  toughness  of 
asparagus,  was  determined  by  chemical  analysis,  and  by  microscopic 
examination  of  the  spears  in  order  to  ascertain  the  degree  of  lignifica- 
tion  of  structural  elements.  These  changes  are  markedly  influenced 
by  the  temperature  at  which  the  spears  are  stored  and  by  the  length 
of  storage  period. 

3.  The  storage  temperatures  employed  were  33°,  41°,  56°,  77°, 
and  95°  F.    All  changes  were  observed  at  24-hour  intervals. 

4.  It  is  known  that  asparagus  spears  grow  in  length  in  the  crate, 
if  the  butts  are  on  moist  moss.  If  the  moss  is  uniformly  moist  and 
remains  so  throughout  the  period  of  storage,  the  chief  factor  deter- 
mining the  growth  rate  is  temperature.  The  growth  rate  of  spears 
with  the  butts  in  water  was  found  to  be  least  at  33°  F.,  and  to 
increase  as  the  temperature  was  raised  (within  the  limits  of  the  experi- 
ment). Mold  appeared  on  the  asparagus  stored  at  temperatures  of 
77°  and  95°  F.,  after  5  and  4  days  respectively,  and  consequently, 
the  results  obtained  at  these  temperatures  after  mold  appeared  are 
discarded.  The  greatest  percentage  of  increase  in  the  length  of 
asparagus  occurred  during  the  first  24  hours,  after  which  there  was  a 
slowing  down  in  the  rate. 

5.  Asparagus  spears  stored  with  their  butts  in  water  or  on  wet 
moss  absorb  water  and  increase  in  weight.  The  rate  of  weight  increase 
due  to  water  absorption,  which  is  also  shown  in  a  decrease  in  the  per- 
centage of  dry  matter,  was  least  at  33°  F.,  somewhat  greater  at  41°  F., 
and  still  greater  at  the  higher  temperatures.  Here,  again,  the  greatest 
percentage  of  increase  in  weight,  or  decrease  in  dry  matter,  occurred 
during  the  first  24  hours  after  the  spears  were  harvested. 

6.  During  the  storage  period  represented  in  these  experiments, 
there  was  a  loss  in  reducing  substances  and  in  total  sugars.     These 


BULL.  410]         FACTORS   INFLUENCING   QUALITY   OF   ASPARAGUS  27 

losses  were  especially  pronounced  at  the  higher  temperatures  (56°, 
77°,  and  95°  F.).  The  maximum  rate  of  loss  occurred  during  the 
first  24  hours.  At  a  temperature  of  33°  F.,  however,  there  was  a  very 
slight  gain  in  the  amount  of  these  substances  during  the  first  24  hours, 
after  which  there  was  a  decrease;  and  at  41°  and  56°  F.,  after  an 
initial  loss  there  was  apparently  a  very  slight  gain  in  these  substances 
during  the  second  day,  after  which  there  was  further  decrease.  It 
should  be  stated  that  sugars  constitute  but  one  group  of  substances 
which  determine  flavor ;  among  others  may  be  mentioned  esters,  gluco- 
sides,  ammo-acids,  and  proteins.  The  loss  of  sugar  during  storage 
is  probably  due  to  its  transformation  to  cell  wall  material,  chiefly 
lignin,  and  other  substances. 

7.  Both  microchemical  and  macrochemical  studies  showed  a  gen- 
eral increase  in  the  amount  of  fiber  of  the  spears  at  all  storage  tem- 
peratures. This  was  shown  in  the  number  of  lignified  elements  both 
in  the  pericycle  and  in  the  vascular  bundles,  as  well  as  in  the  per- 
centage of  crude  fiber  as  ascertained  by  chemical  analysis.  The 
greatest  increase  (with  one  exception)  in  fiber  at  all  temperatures 
came  during  the  first  24  hours  after  the  asparagus  was  cut,  but  was 
least  at  the  lowest  temperature,  and  greatest  at  the  highest  tem- 
perature. In  storage,  lignification  took  place  the  full  length  of  the 
spear. 

8.  It  appears  from  the  results  above,  that  green  asparagus  should 
be  bunched,  packed,  and  placed  under  refrigeration  as  soon  after 
harvest  as  is  compatible  with  efficient  handling.  There  is  progressive 
deterioration,  as  shown  in  the  reduction  in  sugar,  and  increase  in  fiber, 
even  at  a  temperature  slightly  above  the  freezing  point ;  it  is  desirable, 
therefore,  that  the  product  reach  the  consumer  in  the  shortest  possible 
time.  The  results  obtained  show  that  green  asparagus  should  be 
maintained  at  temperatures  slightly  above  the  freezing  point.  It  is 
desirable  that  the  crate  and  the  parchment  wrappers  surrounding  the 
individual  bunches  be  clearly  marked  so  as  to  indicate  to  retailers  and 
consumers  that  fresh  asparagus  should  be  kept  at  a  low  temperature 
in  order  that  its  edible  quality  may  be  maintained. 


28  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


ACKNOWLEDGMENTS 

The  writers  desire  to  express  their  appreciation  to  Mr.  J.  Gordon 
Sewell  of  the  Division  of  Chemistry,  who  helped  in  preparing  the 
samples,  tabulating  data,  and  calculating  the  results  from  the  chemical 
analyses ;  to  Mr.  H.  A.  Borthwick  of  the  Division  of  Botany,  who 
assisted  in  the  microchemical  studies;  and  to  Mr.  H.  W.  Allinger  of 
the  Division  of  Chemistry  and  Mr.  Oscar  H.  Pearson  of  the  Division 
of  Truck  Crops  for  their  careful  work  in  making  the  analyses. 


LITERATURE     CITED 

i  Bitting,  K.  G. 

1917.     Deterioration  in  asparagus.     Nat.   Canners'  Assoc.  Bull.   11:    1-18. 

2  Morse,  F.  W. 

1917.     Experiments   in    keeping   asparagus    after    cutting.      Massachusetts 
Agr.  Exp.  Sta.  Bull.   172:    297-307. 

s  Munson  and  Walker 

1925.     Methods  of  analysis  A.  O.  A.  C,  p.  191. 


lOm-10,'26 


